The human body has many regions in which pressure differences cause matter to move. For example, the human heart pumps blood through the body. Muscles around the alimentary canal apply a pressure to the channel which moves food from the mouth into the stomach. Further, a pressure increase in a portion of the body may be caused by a chemical reaction such as the development of a gas in an enclosed body cavity.
Monitoring pressures in the human body can provide important information about the function of the human body and can be used to detect disorders and diseases or can be used to control a recovery from a disease.'
For example, dysphagia, which is a disorder that causes difficulty in swallowing, typically affects infants and elderly people and is especially prevalent in post-stroke patients. It is difficult to diagnose this disease and diagnostic tools are often very uncomfortable for the patient.
A multi-bore catheter tube is commonly used for diagnose of this disorder and the multi-bore catheter is inserted into the oesophagus. The exit ports of the bores of the catheter are positioned at different locations along the catheter and a steady flow of water exits through each port. Measurement of the hydraulic water pressure at an input of each bore gives an indication of the pressure distribution in the oesophagus and therefore can be used to diagnose the disorder.
Another method of in-vivo pressure measurement involves usage of a series of piezoelectric or electro-mechanical devices. Such devices typically are expensive and require a relatively large number of electrical wires to be contained in a catheter which consequently is of relatively large thickness. The device is inserted through the nose of the patient and its relatively large diameter results in discomfort for the patient.
Recently optical pressure measurement devices became popular in which an external pressure change effects a change in light interference conditions which can be detected. Such an optical device may comprise a fibre Bragg grating which has an optical response that depends on a strain of the Bragg grating. Such strain effected by applying a “squeezing” force around the Bragg grating and the resultant increase in strain will shift a wavelength of an optical response to longer wavelengths.
The present invention provides an alternative technical solution.